[SCSI] atp870u: convert to accessors and !use_sg cleanup

 - convert to accessors and !use_sg cleanup
 - Probably not ready for sg-chaining

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Acked-by: Christoph Hellwig <hch@infradead.org>
Cc: jameshsu <jameshsu@acard.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>